Nanosecond fluorescence techniques including nanosecond time-resolved emission spectroscopy and nanosecond time-resolved anisotropy will be used to investigate the kinetics of several excited-state processes. These include solvent relaxation, proton transfer, energy transfer and the rotational motion of chromophores. The detailed kinetic information available from the fluorescence studies will be used to evaluate solvation at protein binding sites. Naphthols, naphthylamines, and quinolines will be used as new types of fluorescence probes to evaluate the proton donating and accepting character of protein and membrane dye binding sites. Anisotropy measurements will be used to investigate segmental flexibility and subunit association of phosphofructokinase. A similar approach will be used to investigate segmental flexibility in IgG(1) and IgG(2), two antibodies from the guinea pig.